The project will develop a dendritic cell (DC)-based therapeutic vaccine to control the latent HIV-1 reservoir. Infected individuals are subject to life long treatment with antiretroviral drugs. Cessation of treatment results in a rapid rebound of virus loads that is seeded by a long-lived reservoir of latently infected T cells. The project will develop a lentiviral-vector-based, DC-targeted HIV-1 vaccine to address this problem. The approach is a two-pronged strategy that activates provirus expression in latently infected T cells and stimulates an immune response against infected cells to target them for lysis and diminish the size of the latent reservoir, with the goal of allowing patients to stop antiretroviral therapy During the R21 phase, lentiviral vectors will be generated that express HIV-1 antigens such as mosaic Gag that is optimized for CTL epitopes. The vectors will co-express CD40 ligand to increase the antigen presentation activity of the transduced DCs and stimulate antigen- specific T cell responses. The vaccine approach will then be tested in vivo using the bone marrow, liver, thymus (BLT)-humanized mouse model. HIV-infected BLT-mice on antiretroviral drugs will be injected with autologous lentiviral vector-transduced DCs to determine the fate of the transduced DCs, their role in immune activation, and their ability to disrupt the latent reservoir. BLT-mice will also be used to determine whether immunization with transduced DCs boosts HIV-specific T cell responses and facilitates control of rebound viremia following treatment interruption. The R33 phase of the project will test the lentiviral DC vaccines developed in the BLT-model in a non-human primate (NHP) pilot study using SIV-infected pig-tailed macaques. During this expanded phase, the ability of the transduced DCs to stimulate HIV-specific CTLs and target the latent reservoir will also be tested using cells from HIV-infected patients on antiretroviral therapy. The success of these studies will lay the foundation for larger scale NHP studies and clinical trials in humans.